1. Field of the Invention
The present invention relates to a locking device for locking and unlocking the slider rails which is adapted to adjust the fore-and-aft postions of a vehicle seat, and in particular relates to a dual-type one in which a pair of locking devices are respectively provided upon the right and left slide rails.
2. Description of the Prior Arts
By way of example, a typical prior-art and improved locking devices for slide rails are known from the Japanese Patent Publication No. 58-55011, in which an improvement is made as against an external-type locking device which is most commonly used one provided externally of the slide rail, by integrally incorporating the slide rail in the seat frame and arranging a stopper above a lower rail of the slide rail such as to be engagable with the lower rail for locking purpose, whereby the locking device is internally provided in the seat frame and a part of slide rail. This first prior art is made by the inventors of the present invention, and afterwards, they produce a second improved locking device which is know from the Japanese Laid-Open Patent Publication No. 61-295144 wherein the upper rail of the slide rail is comprised of right-half and left-half members, with a stopper being slidably provided within a swollen portion defined between those two half members of the upper rail. According to the second pior art, the stopper is not exposed externally between the two half members of the upper rail.
However, while the inventors witness the success of the above-mentioned second prior art in terms of its slimplified, low-cost structure of the locking device, which is materialized by direct use of the upper rail, and therefore does not require additional members, realizing a weight-light structure, they have found that the related locking device has not yet been improved in simplicity of structure and has remained complicated structurally. When it comes to applying it to the dual-type locking device, the interlocking systems or the associated mechanisms result in being more complicated.